Starch consists of a mixture of amylose (15-30% w/w) and amylopectin (70-85% w/w). Amylose consists of linear chains of α-1,4-linked glucose units having a molecular weight (MW) from about 60,000 to about 800,000. Amylopectin is a branched polymer containing α-1,6 branch points every 24-30 glucose units; its MW may be as high as 100 million.
Sugars from starch, in the form of concentrated dextrose syrups, are currently produced by an enzyme catalyzed process involving: (1) liquefaction (or viscosity reduction) of solid starch with an α-amylase into dextrins having an average degree of polymerization of about 7-10, and (2) saccharification of the resulting liquefied starch (i.e. starch hydrolysate) with amyloglucosidase (also called glucoamylase or GA). The resulting syrup has a high glucose content. Much of the glucose syrup that is commercially produced is subsequently enzymatically isomerized to a dextrose/fructose mixture known as isosyrup.
α-amylases (EC 3.2.1.1) hydrolyze starch, glycogen, and related polysaccharides by cleaving internal α-1,4-glucosidic bonds at random. This enzyme has a number of important commercial applications in, for example the sugar, brewing, alcohol and textile industries. α-amylases are isolated from a wide variety of bacterial, fungal, plant and animal sources. Industrially, many important α-amylases are those isolated from Bacilli. 
For a number of years, α-amylase enzymes have been used for a variety of different purposes, including starch liquefaction, textile desizing, starch modification in the paper and pulp industry, and for brewing. These enzymes also can be used to remove starchy stains during dishwashing and laundry washing.
One Bacillus α-amylase that has been sequenced is that from Bacillus sp. no. 195 (BAA). It consists of two domains: a catalytic domain similar to animal α-amylases and a domain that contains two starch binding motifs. See J. Sumitani et al., “New type of starch-binding domain: the direct repeat motif in the C-terminal region of Bacillus sp. no. 195 α-amylase contributes to starch binding and raw starch degrading,” Biochem. J. 350: 477-484 (2000). In Sumitani et al., (2000), three active forms of the gene products were found in the culture supernatant of Streptomyces lividans, in which the Bacillus sp. no. 195 gene product was expressed heterologously. The three products were a 69 kDa form, a 60 kDa form, and a 50 kDa form. The 69 kDa form appears to be the full size mature protein with the molecular weight equivalent to that calculated based on the nucleotide sequence of the full length gene. The 60 kDa form appeared to be the same as that of the natural enzyme of Bacillus sp. no. 195 and was presumed to be generated by proteolytic processing between the two starch binding motifs located in the C-terminus. This form had lower activity for raw starch binding and degradation as compared to the 69 kDa form. The 50 kD form cannot bind or degrade insoluble starches.
Amylases have been used in textile processing, laundry and cleaning compositions, desizing compositions, and in baking, starch liquefaction and processing. Thus, there is a continuing need to identify α-amylases that are easier to produce at reduced costs, improve cost margins, deliver plant capacity savings, and higher activity products.